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arXiv · 2610.05927

Tunable low-phase-noise terahertz synthesis using a fiber-interferometer-referenced optical frequency comb and an EDFA-integrated Vernier cavity

Masayuki Higaki·Yoshiaki Nakajima·Yu Tokizane·Kwangyun Jung·Ryosuke Nakamura·Naoya Kuse·Takeshi Yasui
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Abstract

demonstrate a frequency-tunable, low-phase-noise terahertz (THz) synthesizer based on a fiber-interferometer-referenced optical frequency comb (OFC), an erbium-doped fiber amplifier (EDFA)-integrated Vernier cavity, and dual optical injection locking (OIL). The Vernier cavity converts the densely spaced modes of a fiber OFC with a repetition frequency of approximately 100 MHz into a filtered comb with gigahertz-scale effective mode spacing, facilitating selective single-mode OIL. Intracavity and extracavity EDFAs in the Vernier cavity enable a side-mode suppression ratio exceeding 70 dB. Independent control of the Vernier-cavity free spectral range and the OFC repetition frequency provides flexible Vernier filtering conditions for selecting master modes for dual OIL. Two selected comb modes are transferred to injection-locked optical carriers and photomixed in a uni-traveling-carrier photodiode to generate continuous-wave THz signals. Frequency-tunable THz generation is demonstrated at 230, 267, and 320 GHz. At 267 GHz, a signal-to-noise ratio exceeding 70 dB and a measured phase noise of -95.7 dBc/Hz at a 10-kHz offset are obtained; the phase-noise measurement is limited by the local-oscillator system. The proposed architecture provides a fiber-based approach to frequency-tunable, low-phase-noise THz synthesis by combining an optical-reference-based OFC with flexible Vernier-assisted comb-mode selection.

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Masayuki Higaki, Yoshiaki Nakajima, Yu Tokizane, Kwangyun Jung, Ryosuke Nakamura, Naoya Kuse, Takeshi Yasui. 2026-10-05. Tunable low-phase-noise terahertz synthesis using a fiber-interferometer-referenced optical frequency comb and an EDFA-integrated Vernier cavity. https://arxiv.org/abs/2610.05927

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